Genetic analysis of drought stress adaptation in bread wheat diversity

Abstract

The accumulations of proline (Pro) and hydrogen peroxide (H₂O₂) are the typical response of plant against drought stress, therefore genetic analysis of these responses are crucial to establishing new varieties in crops like wheat. A genetic study namely genome-wide association study (GWAS) was performed to elucidate loci and candidate genes linked to drought-induced Pro and H₂O₂ accumulation and H₂O₂-induced root-shoot growth in bread wheat. GWAS identified a total of 11 significant marker-trait associations (MTAs) on 1A and 1B chromosomes for relative Pro values in a glasshouse experiment. The same study was performed in the field environment, and the study identified the most significant MTAs on 5B, and 1B chromosomes associated with 71 and 34 markers for Pro and H₂O₂ stress tolerance index (STI), respectively. The GWAS was also performed for H₂O₂-induced root-shoot variability to identify linked candidate loci and genes. Significant MTA was identified on 3B, 2A, 5A, 3B, 5D, 5A, and 6B chromosomes for relative root length, STI root length, relative shoot length, STI shoot length, relative root fresh weight, relative shoot fresh weight, STI shoot fresh weight, respectively. Linkage disequilibrium analyses revealed that European cultivars are linked with higher Pro accumulation under drought conditions. An opposite outcome between European and Non-Europe cultivars was observed for STI of Pro and H₂O₂. Similarly, distinct genetic relatedness was observed between the traditional and modern cultivars for root-shoot-associated STI and relative values. Minor alleles of single-marker and haplotypes were associated with higher Pro and H₂O₂ accumulation under drought and also with higher STI and the relative value for root-shoot traits. The candidate genes identified in significant loci regions were mostly involved in metal ion binding, transmembrane transport, oxidation-reduction process, protein phosphorylation, protein kinase, DNA, and ADP binding processes. The candidate loci, homolog search, and protein amylases revealed the loci and genes identified for drought-induced Pro and H₂O₂ and H₂O₂-induced root-shoot traits are reported first time in wheat. The alleles showed the contrasting phenotype that could be utilized to understand precisely their role under drought. Collectively, identified genetic factors associated with Pro and H₂O₂ biosynthesis lays a fundamental basis for future functional characterization of the identified genes.